As compared with a traditional liquid crystal panel, an AMOLED (Active Matrix Organic Light Emitting Diode) panel has characteristics of rapider response speed, higher contrast, wider angle of view and the like, therefore the AMOLED has been get an increasing attention of display device developers.
An Active Organic Light Emitting diode is driven by a pixel circuit to emit light. A traditional 2T1C pixel circuit is composed of tow transistors (TFTs) and one capacitor (C), and as illustrated in FIG. 1, particularly comprises a driving transistor DTFT, a switching transistor T5′ and a storage capacitor Cst. The switching transistor T5′ is controlled by a scan line signal Vscan, and is configured to control inputting of a data voltage Vdata, the driving transistor DTFT is configured to control the Organic Light-Emitting Diode (OLED) to emit light, and the storage capacitor Cst is configured to provide a sustaining voltage for a gate of the driving transistor DTFT.
FIG. 2 is a driving timing chart of the 2T1C pixel circuit shown in FIG. 1. An operation process of the 2T1C pixel circuit is as follows. When the scan signal is at a low level, the switching transistor T5′ is turned on, a gray scale voltage on a data line charges the storage capacitor Cst, meanwhile the data voltage Vdata is applied to the gate of the driving transistor DTFT, so that the driving transistor DTFT operates in a saturation state and drives the Organic Light-Emitting Diode OLED to emit light. When the scan signal is at a high level, the switching transistor T5′ is turned off, the storage capacitor Cst provides the sustaining voltage to the gate of the driving transistor DTFT, so that the driving transistor DTFT is still in the saturation state and the OLED goes on to emit light.
It can be seen from above that the OLED in the AMOLED can emit light because it is driven by a driving current generated by the driving transistor DTFT operating in the saturation state, and more particularly the driving current (namely a current flowing through the OLED) can be represented by IOLED=K(Vgs−|Vthd|)2, where Vgs is a voltage difference between the gate and a source of the driving transistor DTFT, |Vthd| is a threshold voltage of the driving transistor DTFT, and K is a constant associated with a structure of the driving transistor DTFT per se and the manufacturing process. Because the uniformity in the threshold voltages Vth of the transistors is poor in the existing Low Temperature Poly-Silicon process and the threshold voltage would shift during a usage process, different threshold voltages of the driving transistors DTFT would generate different driving currents although the same data voltage Vdata is applied to the driving transistors DTFT, such that the uniformity in the brightness on the AMOLED panel is poor.
Recently, a touch control function has been applied more widely in various display panels, especially in a mobile display, and nearly becomes a standard configuration for a smart phone. In the prior art, a display panel and a Touch Screen Panel (TSP) are manufactured separately at first, and then are fixed together. Such process leads to a complex process and a high cost for the panel to realize both of a display function and a touch control function, and is helpless for producing a lighter and thinner touch panel. TST in cell technique integrates the display function and the touch control function, and may be accomplished only by one process instead of two processes, therefore it not only has advantages such as low cost but also can simplify the process and make the touch panel be lighter and thinner. However, no solution is proposed so far regarding how to integrate a touch control circuit and the pixel circuit perfectly.